In the manufacture of fluorescent lamps, the lamp envelope is usually provided with a base at each end. Generally, the base comprises a shell secured to an end of the lamp envelope. An insulating disk is fixed in the shell and carries a pair of hollow pins into which the lamp lead wires are secured, such as by welding or soldering for example. The lamp is supported by a pair of suitable lamp holders or sockets into which the lamp bases extend for connection to a source of electrical energy. Such lamps are generally called bi-pin base lamps and are among the most common designs.
Occasionally, the starting and/or electrical characteristics of certain fluorescent lamps are such that, in designing a base, consideration must be given to the inclusion of safety features to eliminate the danger of electrical shock. At least one such lamp type is known by its base, which is called a recessed double contact or RDC type. One such lamp and base are shown in U.S. Pat. No. 2,896,187.
The latter lamps tend to be more expensive than the bi-pin type, in part because of the expense of maintaining an inventory of two different types of bases.